Oscillating radioreceiver



March 13, 1934. sco 1,950,752

OSCILLATING RADIORECEIVER Filed July 18, 1932 INVENTOR,

P /P F. COF/ELD. /{W

ATTORNEY Patented Mar. 13, 1934 OSCELLATING RADHGRECEIVER Application July 18, 1932, Serial No. 623,113

3 Claims.

My invention relates to radio receivers, and particularly to receivers for continuous wave telegraph systems, although it is also applicable to the reception of modulated signals by the 5 zero beat method.

Among the objects of my invention are: to provide an oscillating receiver wherein full wave rectification of the mixed incoming and locally generated oscillation is obtained; to provide a receiver wherein both heterodyne amplification and cascade amplification or the received signals is accomplished in the oscillator circuit; to provide a receiver which is stable in operation, and wherein the oscillator displays the advantages of balanced tube connection; and to provide a receiver wherein a major portion of th high frequency component of the detected signals is excluded from the output circuit.

Other objects of my invention will be apparent or will be specifically pointed out in the description forming a part of this specification, but I do not limit myself to the embodiment of my invention herein described, as various forms may be adopted within the scope of the claims.

My invention can best be understood from reference to the accompanying drawing, which comprises a schematic diagram of a receiver embodying the invention.

Considered broadly, my invention comprises an oscillator of the type wherein a pair of oscillating tubes are connected in Opposite phase relation, the plate of each tube supplying potential to control the grid of the other tube. The incoming signal is applied to the plate of one of these tubes, and hence to the grid of the other,

thus affecting both tubes cooperatively. A detector tube, preferably having a pair of grids or control elements each having substantially equal control upon the space current of the tube and afiecting this space current in the same sense, is connected so that one of the control elements is supplied from each of the oscillator plates. The usual condenser and leak are supplied for each of the control elements, so that the detector operates by grid rectification. As a result of this connection, the two grids vary in potential in opposite directions insofar as the high frequency applied thereto is concerned, and the resultant high frequency change upon the space current or" the detector tube is substantially nil. The grid rectification current, however, varies in the same manner and in the same phase upon both of the control electrodes, with the result that the output of the tube is substantially pure low frequency, without the intervention of filters.

In the form of the invention shown in the diagram the usual antenna system 1 affects a radio frequency amplifier 2 through the conventional radio frequency transformer tuned by a variable condenser 5. The filament 6 and control electrode '7 of the amplifier tube are connected across the secondary of the radio frequency transformer 4 in the usual manner. The plate 9 of the tube 2 connects through an inductance l0 and radio frequency choke coil 11 with a plate battery or other potential source 12, whose negative end connects with the filament.

The inductance coil 10 is one of a pair of similar coils, which are preferably positioned or shielded so as to have zero mutual inductance, and which are bridged by a variable condenser 14. The two inductance coils 10 and the condenser form the tuned circuit of the heterodyne oscillator, the choke coil 11 being connected preferably at the mid-point between the two coils, and supplying plate current to the plates 15 and 15' of a pair of similar vacuum tubes 16.

A lead 1'? connects from the plate 15, through a grid condenser or blocking condenser 19, with the control electrode 20 of the tube 16. In like manner there is a connection from the plate 15 through a second condenser 19 to the control electrode 20 of the tube 16. Grid resistors 21 connect from each control electrode to a common filament circuit 22 for all of the tubes.

Each of the plates 15, 15 connects through a grid condenser 24 with one of the control electrodes 25 of a detector tube 26. This tube may be one of the type wherein two insulated grids are interwound in the same plane, but it is preferably of the type described in the copending application of Ralph M. Heintz, filed July 18, 1932, Serial No. 623,138, entitled Thermionic tube. In this tube two coordinate plate-like control electrodes are mounted in the same plane, on the opposite side of the cathode from the plate, each acts upon the electron stream to affect it in the same sense. The tube 26 may, however, be a tetrode of the ordinary type, or even a triode coupled to the amplifier output so that the two oscillator tubes affect it cooperatively. These last two possible connections are not as satisfactory as the recommended connection shown, however.

The plate 27 of the detector tube connects through the primary of an output transformer 29 and plate potential source so to the common filament circuit 22. The secondary 31 of the output transformer may connect through output leads 32 to an audio frequency amplifier or any other desired work circuit.

It will be seen that the incoming signals and the oscillating potential of the plate 15 are applied in parallel to one of the control electrodes of the tube 26. At the same time these signals are applied to the grid of the tube 16, and are amplified by this tube, reversing phase in the process, to be applied to the other grid of the tube 26. The tube 16' therefore acts as an additional amplifier tube for the incoming signals.

The potentials on the two grids 24: are swung in opposite directions by the incoming signals, each of these control electrodes becoming positive during a portion of the cycle when the other grid is negative. During the time when the grid is positive it collects electrons, which leak off through the grid leak 23, the fall of potential in these leaks providing a negative bias to the grid which reduces the space current. The amount of the positive swing depends upon the amplitude of the signals impressed upon the grid, the bias of the two grids varying together at audio frequency to provide the usual grid detection current. Since a positive swing of one grid is accompanied by an equal and opposite negative swing of the other grid, the mean space current does not change at radio frequency, and hence the usual by-pass condenser around the transformer primary 29 is unnecessary.

I claim:

1. In an oscillating receiver for radio waves, an oscillator comprising a pair of vacuum tubes connected to cooperate in opposite phase relation, a

detector tube having a pair of control electrodes each affecting the space current of said detector tube in the same sense, means for applying potential from each of said pair of vacuum tubes to one of said control electrodes, and means for simultaneously applying an incoming signal to one of said control electrodes.

2. In an oscillating receiver for radio waves, an oscillator comprising a pair of vacuum tubes connected to cooperate in opposite phase relation, an input circuit connected in parallel with one of said tubes and in cascade with the other of said tubes, a detector tube having a pair of control electrodes each affecting the space current of said detector tube in the same sense, and means for applying potential from the output of each of said oscillator tubes upon a corresponding control electrode of said detector tube.

3. In combination, a pair of oscillator tubes, an oscillating circuit connecting the plates of said tubes, a connection between the plate of each of said tubes and the control electrode of the other, an amplifier tube having a plate connected in parallel with the plate of one of said oscillator tubes, whereby said amplifier is also connected in cascade with the other of said oscillator tubes, and a detector having a pair of similar control electrodes, each of said control electrodes being connected to the plate of one of said oscillator tubes.

PHILIP F. SCOFIELD. 

